Theresa May accused Russia of preventing international inspectors from reaching the site of the Syrian chemical weapons attack as relations with Moscow deteriorated further.

A diplomatic storm erupted as the Office for the Prohibition of Chemical Weapons (OPCW) said Syrian and Russian officials had claimed there were “security issues” which prevented a fact-finding mission from reaching Douma, where around 75 people are thought to have died in the attack.

Russia suggested the missile strikes launched by the UK, US and France were part of the reason why the chemical weapons watchdog could not travel to the scene of the attack.

It strongly denied interfering with the work of inspectors attempting to reach the site of the atrocity which the UK and Western allies have concluded was perpetrated by the regime of Moscow’s ally Bashar Assad.

Russian foreign minister Sergey Lavrov said relations between Moscow and the West were worse than at the time of the Cold War.

He said the UK, Nato and European Union had closed the normal channels of communication with Russia which provided safeguards against confrontation.

“I think it is worse, because during the Cold War there were channels of communication and there was no obsession with Russophobia, which looks like genocide by sanctions,” he told the BBC.

If you go to a site which was just bombed I imagine you might have certain logistic problems. And there are no Western guarantees of no more strikes, only words. That is why Russia was pushing for UNSC resolution to support OPCW mission on the eve of US-UK-FR attack

Russian officials at the OPCW said later that arrangements were being made for inspectors to visit Douma on Wednesday.

However, updating MPs on the military action, the Prime Minister said it would not have been worth waiting for their findings because Russian vetoes at the United Nations meant no blame could be apportioned for the attack.

“Even if the OPCW team is able to visit Douma to gather information to make that assessment – and they are currently being prevented from doing so by the regime and the Russians – it cannot attribute responsibility,” she said.

Mrs May accused Russia and Syria of attempting to cover up the attack.

“The Syrian regime has reportedly been attempting to conceal the evidence by searching evacuees from Douma to ensure samples are not being smuggled from this area and a wider operation to conceal the facts of the attack is under way, supported by the Russians,” she told MPs.

Men load a carpet and mattress on to a bicycle in front of damaged buildings in the town of Douma (Hassan Ammar/AP)

At a meeting of the OPCW in The Hague, director-general Ahmet Uzumcu said the organisation’s team had arrived in Damascus on Saturday but “has not yet deployed to Douma”.

“The Syrian and the Russian officials who participated in the preparatory meetings in Damascus have informed the FFM (fact-finding mission) team that there were still pending security issues to be worked out before any deployment could take place.”

The UK’s representative Peter Wilson said: “It is imperative that the Syrian Arab Republic and the Russian Federation offer the OPCW fact finding mission team their full co-operation and assistance to carry out their difficult task.”

Russian diplomat Dmitry Polyanskiy said “all the obstacles” for the OPCW mission were the result of the US, UK and French “aggression” and the possibility of further strikes.

Mr Polyanskiy, Russia’s first deputy permanent representative at the UN, said: “If you go to a site which was just bombed I imagine you might have certain logistic problems. And there are no Western guarantees of no more strikes, only words.”

Relations between Russia and the UK have been plunged into the deep freeze following the nerve agent attack on Sergei and Yulia Skripal in Salisbury.

Mr Lavrov denied Russia had “tampered” with the site of the Syrian attack and insisted there was no proof that chemical weapons had been used.

The Russian foreign minister told the BBC: “There is no proof that on April 7 chemical weapons were used in Douma.

“I cannot be impolite to the heads of other states … but frankly speaking, all the evidence they quoted was based on media reports and social networks.”

Labour leader Jeremy Corbyn repeated his assertion that the military action was “legally questionable”.

There were cries of “shame” from the Tory benches as he told Mrs May she “is accountable to this Parliament, not to the whims of the US President”.

And shadow attorney general Baroness Chakrabarti questioned the Government’s justification for the airstrikes, telling BBC Radio 4’s Today programme: “You can’t use force under international law just to punish Syria for bad behaviour.”

Four Royal Air Force Tornado GR4s joined the co-ordinated missile strikes at 2am on Saturday, launching Storm Shadow missiles at a base 15 miles west of Homs.